While today’s computer networks support only best-effort service, future packet-switching integrated-services networks will have to support real-time communication services that allow clients to transport information with performance guarantees expressed in terms of delay, delay jitter, throughput, and loss rate. An important issue in providing guaranteed performance service is the choice of the packet service discipline at switching nodes. In this paper, we survey several service disciplines that are proposed in the literature to provide per-connection end-to-end peqormance guarantees in packet-switching networks. We describe their mechanisms, their similarities and differences, and the performance guarantees they can provide. Various issues and tradeoffs in designing service disciplines for guaranteed performance service are discussed, and a general framework for studying and comparing these disciplines are presented. I.

We review some recent results regarding the problem of providing deterministic quality of service guarantees in slot-based virtual circuit switched networks. The concept of a service curve is used to partially characterize the service that virtual circuit connections receive. We find that service curves provide a convenient framework for managing the allocation of performance guarantees. In particular, bounds on end-to-end performance measures can be simply obtained in terms of service curves and burstiness constraints on arriving traffic. Service curves can be allocated to the connections, and we consider scheduling algorithms that can support the allocated service curves. Such an approach provides the required degree of isolation between the connections in order to support performance guarantees, without precluding statistical multiplexing. Finally, we examine the problem of enforcing burstiness constraints in slot-based networks.

This paper addresses the problem of providing per-connection end-to-end delay guarantees in a highspeed network. We assume that the network is connection oriented and enforces some admission control which ensures that the source traffic conforms to specified traffic characteristics. We concentrate on the class of Rate-Controlled Service Disciplines, in which traffic from each connection is reshaped at every hop, and develop end-to-end delay bounds for the general case where different reshapers are used at each hop. In addition, we establish that these bounds can also be achieved when the shapers at each hop have the same "minimal" envelope. The main disadvantage of this class of service disciplines is that the end-to-end delay guarantees are obtained as the sum of the worst case delays at each node, but we show that this problem can be alleviated through "proper" reshaping of the traffic to an envelope, which is in general different from the original envelope of the source traffic. We illustrate the impact of this reshaping by demonstrating its use in designing Rate-Controlled Service disciplines that outperform GPS-based service disciplines. Furthermore, we show that we can restrict the space of "good" shapers to a family which ischaracterized by only one parameter. We also describe extensions to the service discipline that makeitwork conserving, and as a result reduce the average end-to-end delays.

To support the requirements for the transmission of continuous media, such as audio and video, multiservice packet switching networks must provide service guarantees to connections, including guarantees on throughput, network delays, and network delay variations. For the most demanding applications, the network must offer a service which can provide deterministic guarantees for the maximum delay ofpackets from all connections, referred to as bounded delay service. The admission control functions in a network with a bounded delay service must have available schedulability conditions that detect violations of delay guarantees in a network switch. In this study, exact schedulability conditions are presented for packet switches which transmit packets based on an Earliest-Deadline-First (EDF) or a Static-Priority (SP) algorithm. The schedulability conditions are given in terms of a general traffic model, making the conditions applicable to a large class of traffic specifications. A comparison of the new schedulability conditions with existing, less accurate, conditions show the e ciency gain obtained by using exact conditions. Examples are presented that show how the selection of a particular traffic specification and a schedulability condition impact the efficiency of a bounded delay service.

Motivated by recent development in high speed networks, in this paper we study two types of stability problems: (i) conditions for queueing networks that render bounded queue lengths and bounded delay for customers, and (ii) conditions for queueing networks in which the queue length distribution of a queue has an exponential tail with rate `. To answer these two types of stability problems, we introduce two new notions of traffic characterization: minimum envelope rate (MER) and minimum envelope rate with respect to `. Based on these two new notions of traffic characterization, we develop a set of rules for network operations such as superposition, input-output relation of a single queue, and routing. Specifically, we show that (i) the MER of a superposition process is less than or equal to the sum of the MER of each process, (ii) a queue is stable in the sense of bounded queue length if the MER of the input traffic is smaller than the capacity, (iii) the MER of a departure process from a stable queue is less than or equal to that of the input process (iv) the MER of a routed process from a departure process is less than or equal to the MER of the departure process multiplied by the MER of the routing process. Similar results hold for MER with respect to ` under a further assumption of independence. These rules provide a natural way to analyze feedforward networks with multiple classes of customers. For single class networks with nonfeedforward routing, we provide a new method to show that similar stability results hold for such networks under the FCFS policy. Moreover, when restricting to the family of two-state Markov modulated arrival processes, the notion of MER with respect to ` is shown to be

Variable bit-rate (VBR) compressed video traffic is expected to be a significant component of the traffic mix in integrated services networks. This traffic is hard to manage because it has strict delay and loss requirements while simultaneously exhibiting burstiness at multiple time scales. We show that burstiness over long time scales, in conjunction with resource reservation using one-shot traffic descriptors, can substantially degrade the loss rate, end-to-end delay, and statistical multiplexing gain of a connection. We use large-deviation theory to model the performance of multiple time-scale traffic and to motivate the design of renegotiated constant bit rate (RCBR) service. Sources using

We propose a class of non-work-conserving service disciplines, called the Rate-Controlled Service Disciplines. When coupled with suitable admission control algorithms, Rate-Controlled Service Disciplines can provide end-to-end deterministic and statistical performance guarantees on a per-connection basis in an arbitrary topology packet-switching network. The key feature of a rate-controlled service discipline is the separation of the server into two components: a rate-controller and a scheduler. This separation makes it possible to obtain end-to-end performance characteristics by applying single node analysis at each switch. It also has several other distinct advantages: it decouples the allocation of bandwidths and delay bounds, uniformly distributes the allocation of buffer space inside the network to prevent packet loss, and allows arbitrary combinations of rate-control policies and packet scheduling policies. Rate-controlled service disciplines provide a general framework w...

In this paper we identify the challenges and open issues involved in providing quality-of-service (QOS) guarantees to sessions in a high-speed wide area network and briefly survey research in this area. Four approaches towards providing QOS guarantees are described and discussed: the tightly controlled approach, the approximate approach, the bounding approach, and the observation-based approach.

Compressed digital video is one of the most important traffic types in future integrated services networks. However, a network service that supports delay-sensitive video imposes many problems since compressed video sources are variable bit rate (VBR) with a high degree of burstiness. In this paper, we consider a network service that can provide deterministic guarantees on the minimum throughput and the maximum delay of VBR video traffic. A common belief is that due to the burstiness of VBR traffic, such a service will not be efficient and will necessarily result in low network utilization. We investigate the fundamental limits and tradeoffs in providing deterministic performance guarantees to video and use a set of 10 to 30 minute long MPEG-compressed video traces for evaluation. Contrary to conventional wisdom, we are able to show that, in many cases, a deterministic service can be provided to video traffic while maintaining a reasonable level of network utilization. We first conside...

Information theory has not yet had a direct impact on networking, although there are similarities in concepts and methodologies that have consistently attracted the attention of researchers from both fields. In this paper, we review several topics that are related to communication networks and that have an information theoretic flavor, including multiaccess protocols, timing channels, effective bandwidth of bursty data sources, deterministic constraints on datastreams, queueing theory, and switching networks. Keywords--- Communication networks, multiaccess, effective bandwidth, switching I. INTRODUCTION Information theory is the conscience of the theory of communication; it has defined the "playing field" within which communication systems can be studied and understood. It has provided the spawning grounds for the fields of coding, compression, encryption, detection, and modulation and it has enabled the design and evaluation of systems whose performance is pushing the limits of wha...